BARBER: HEREDITY IN CERTAIN MICRO-ORGANISMS. 47 



vantage over the ordinary plate method, in that the process 

 requires much less time, and one can follow the development 

 of a micro-organism from the first, and be sure that the sub- 

 sequent colony comes from the cell originally isolated. In 

 old cultures a considerable proportion of cells may be dead 

 in the material from which such isolations are made, so it is 

 sometimes necessary to isolate a considerable number of them 

 to obtain a single successful growth. It is possible to work 

 with relatively small quantities of medium in making isola- 

 tions, and I have obtained sufficient sterile serum for this 

 purpose from small blister made on the hand. It seems 

 probable by this method of isolation something may be done 

 in the way of isolating organisms which are with difficulty 

 handled by ordinary methods. I have as yet made but few 

 experiments in this direction. 



The method has been used by several of my students as 

 well as by myself, and they have found it not difficult to 

 acquire. In this description I have omitted many details 

 which would require too much space to describe, but knowl- 

 edge of these are soon acquired by the experimenter. 



I take this opportunity of recognizing the very material 

 assistance rendered me by my students in this work, especially 

 Mr. A. H. Sellards, who has cooperated in many ways, and 

 Mr, Montrose Burrows, who assisted much in designing the 

 pipette holder described above. I wish to acknowledge also 

 the kindness of Doctor Fernbach and other workers at the 

 Pasteur Institute, who placed at my disposal cultures and 

 other laboratory facilities during my work in Paris, in the 

 summer of 1904. 



